With development of technology, dimensions involved in manufacturing fields come to nanometer level from micrometer level. In the process, high precision micro-stages play the roles of nanometer level positioning and machining A nanometer precision micro-stage generally refers to a motion platform with a stroke on the order of millimeter and a precision up to nanometer. In the development of nanometer precision micro-stage driving technology and supporting technology, the following ever existed: piezoelectric ceramic driven flexible hinge supported micro-stage, short stroke voice coil motor driven air floating supported micro-stage and Lorenz motor driven magnetic suspension supported micro-stage.
Piezoelectric ceramic in combination with flexible hinge is a common means for realizing micro-motion which features compact structure, small volume and high displacement resolution. However, the piezoelectric ceramics has a shortage that it moves only within a small range. A 100 millimeter long piece of piezoelectric ceramic is usually required to generate a displacement of 100 micrometer. Piezoelectric ceramics suffer bad characteristics such as hysteresis, creeping and nonlinearity under electric field, which makes their repeatability reduced and transient response slowed down, and their displacement characteristic is also influenced directly by signal frequency, load and history conditions.
Short stroke voice coil motor driven air floating micro-stages overcome traditional contact guide's inability of high precision positioning under high speed and high acceleration, and are widely used in single DOF or plane structures due to their inherent zero friction, low power dissipation, cleanness and excellent dynamic response characteristics. In order to realize six DOF, short stroke voice coil motor driven, air floating micro-stages, it usually adopts a multiple stage structure in which a plurality of layers are connected one by one in series, resulting in a bulky structure, increased inertia for micro-stages and extended time for achieving stabilization. Air floating micro-stages are also difficult to be used in vacuum environment.
Lorenz motor driven, magnetic suspension micro-stages are new type of micro-stages, which are directly driven by electromagnetic force, in which electromagnetic field functions to generate a force perpendicular to the direction of object surface and current in coils is controlled in terms of magnitude to control the magnitude of electromagnetic force, so as to support and drive micro-stages to undergo precise micro-motion. Since a magnetic suspension micro-stage uses contactless magnetic suspension driving technique for both motion platform and driving mechanism, there is no frictional force or wear and tear of machinery parts. Compared with air floating micro-stages, magnetic suspension micro-stages are characterized by silence and no high-frequency vibration and it omits complex structures and components such as gas path and air supply in air floating support, having advantages in terms of strokes, precision and multi-DOF realization. Depending on generation of electromagnetic force, magnetic suspension micro-stages are usually classified into those driven based on Lorentz principle and those driven based on variable magnetic resistance principle, and further classified into moving coil type and moving iron type in terms of arrangement.
Chinese Patent of Invention ZL 200710118130.5 disclosed a six-DOF micro-stage constructed by a three-DOF planar motor and three short stroke voice coil motor drivers in vertical direction with a parallel topology, which breaks through the limitation of piezoelectric ceramics driving, flexible hinge supporting six-DOF micro-stages which were used earlier or the limitation of a multi-level cascading mode of an air floating supporting short stroke voice coil motor, and which realizing significant innovation in structure design. However, the six-DOF micro-stage uses a combination structure of three-DOF in horizontal direction and three-DOF in vertical direction, in which two layers of permanent magnets on top of each other are used in horizontal direction and three short stroke voice coil motors are used in vertical direction, which makes the six-DOF micro-stage have a still complex structure.